Heretofore, applying electrokinetic phenomena such as electrophoresis and electroosmosis to displays has been proposed. Regarding an electrophoretic display, a basic concept thereof has been proposed first in Japanese Examined Patent Publication JP-B2 50-15115 (1975), in which the position of fine particles dispersed in an insulating dispersion is kept under field control to thereby vary the optical reflectivity characteristic of a display apparatus. In Japanese Unexamined Patent Publication JP-A 64-86116 (1989), a technique of sealing up a large number of the open pores of a meshed or porous, open-pored spacer with an electrophoretic particles-containing dispersion has been introduced as a related art, and a method of encapsulating the dispersion in microcapsules has been proposed.
Apart from this, an electroosmotic display is disclosed in Japanese Examined Patent Publication JP-B2 61-34648 (1986). Herein, proposed is a method of controlling the rate of liquid impregnation into a porous material through electroosmosis to thereby obtain a contrast of a display apparatus.
The display apparatus disclosed in JP-B2 50-15115 has an essential problem relating to the life thereof in that the characteristics of the apparatus may be deteriorated owing to the aggregation or sedimentation of the particles in the dispersion. The display apparatus disclosed in JP-A 64-86116 may be improved in point of the problem of aggregation or sedimentation of the particles, but its problem to be solved in point of the life and the driving voltage thereof still remains unsolved. The electroosmotic system disclosed in JP-B2 61-34648 has some problems to be solved in point of the liquid evaporation, the contrast insufficiency, the complicated apparatus structure and the uniformity, and cannot as yet be put into practical use.